If you ignore the genocide issue, it was still a settlement. People came to claim land, at great personal risk. Some of them came seeking material wealth. A few came for more abstract reasons, settling on a religious mission or to escape conflict back in Europe. In their isolation, there was a cultural change - the society that emerged had different values from the old, far more individualistic and anti-authoritarian, culminating in the American Revolution.
Sure it does. Some people still find the old sci-fi dreams inspirational. They are terribly inaccurate dreams, it is true - but they are an ideal to aspire to, not something one might reasonably expect to achieve. Robots in space are a little bit exciting, and they do advance scientific knowledge. A worthfile aim in itsself, but that is all they can do. Human expansion promises new worlds. Not very good worlds, and the process of settling them is going to cost trillions of dollars and more than a few human lives, but it is also something really worth being excited over. There's a whole solar system out there, including a couple of miserable lumps of rock that can potentially be made livable. You don't need a strict economic justification for some things: You go there because it's a part of human nature. Virgin territory, however inhospitable, begs to be tamed. Beyond that, it's just a matter of time, money, and enough foolhardy people willing to go first and do the construction work.
If someone were to invent a magic techno-thingie tomorrow that made travel to Mars affordable, do you think people wouldn't go?